1. Field of the Invention
The present invention relates to a semiconductor device that uses a polycrystalline semiconductor film such as a polysilicon film.
2. Background Art
Polysilicon film is one of thin-film materials widely used in the processes for manufacturing semiconductor devices. Since polysilicon film with low resistance can be easily formed by doping of impurity, polysilicon can be easily processed to form fine patterns, and polysilicon is thermally stable and provides high freedom for heat treatment, the polysilicon film is used in high-precision resistor elements, electrodes for bipolar transistors, TFTs (thin film transistors), or polysilicon diodes and the like.
In the processes for manufacturing semiconductor devices, provision of constant qualities, that is, provision of semiconductor devices with same characteristics is required. In the case of a semiconductor device with polysilicon film, since the quality of the polysilicon film affects the characteristics of the elements, providing the films with even quality is one of the issues in the manufacturing processes.
However, since the properties of silicon grains varies due to doping of impurities or heat treatment, it is difficult to provide same conditions for the factors that determine the quality of polysilicon film, such as grain diameter of polysilicon and inter-grain states. In particular, when a polysilicon films are formed using a plurality of polysilicon depositing apparatuses, or when a polysilicon depositing apparatus is replaced, properties of the manufactured elements may vary depending on manufacturing apparatuses.
Although it has been known as methods of observing polysilicon grains to observe the structure or to measure grain diameters using a transmission electron microscope or a scanning electron microscope, these methods have difficulties for quantification, and are unsuitable for the process control in mass production.
The present invention provides a method for manufacturing a semiconductor device. The method includes these processes below. First, a polycrystalline semiconductor film is formed on a semiconductor substrate. Then, the thickness of the polycrystalline semiconductor film is measured. Next, an impurity is introduced in the polycrystalline semiconductor film, and a part of the impurity is activated by heat treatment. After the heat treatment, the sheet resistance of the polycrystalline semiconductor film is measured. Then the conditions of forming the polycrystalline semiconductor film is adjusted so that the product of the film thickness and the sheet resistance becomes a predetermined value.
The present invention also provides the semiconductor device, such as a resistor element, a transistor and a diode. The polycrystalline semiconductor film is preferably used as an electrode.
Other and further objects, features and advantages of the invention will appear more fully from the following description.